The polycrystalline silicon can be produced according to the monosilane process or the Siemens process. The apparatus according to the invention can also be used with both methods. The methods substantially differ in the reaction partners, with which the polycrystalline silicon is produced.
In the Siemens process, trichlorosilane (SiHCl3) is thermally decomposed in presence of hydrogen on heated high-purity silicon rods at 1000 to 2000° C. The pure silicon is thereby deposited onto the rods. The hydrogen chloride released in the process is fed back into the production. The process takes place at a pressure of approximately 6.5 bar.
In the monosilane process, monosilane (SiH4) is thermally decomposed in presence of hydrogen on heated high-purity silicon rods at 850 to 900° C. The pure silicon grows is thereby deposited onto the rods. The monosilane process takes place at a pressure of approximately 2 to 2.5 bar.